Within semiconductor substrate manufacturing, a chemical mechanical polishing (CMP) process may be used to remove various layers, such as silicon, oxides, copper, or the like. Such polishing (e.g., planarization) may be accomplished by pressing a rotating substrate held in a holder (e.g., polishing head or carrier) against a rotating polishing pad while a slurry is applied ahead of the substrate (e.g., patterned wafer). The slurry is commonly made up of a mixture of oxidants, metal oxide abrasive particles, etchants, complexing agents, and corrosion inhibitors. Thus, during polishing, a continuous process of oxidation by oxidants and material removal by abrasive particles and etchants is carried out by the slurry and polishing process. During this polishing process, precise control of the amount of material removal from the substrate is sought. However, given the limitations of existing processes, it is difficult to achieve uniformity, especially for removal of small layer thicknesses.
Accordingly, improved polishing apparatus, systems, and methods are sought.